It's simplistic to attempt to attribute the Cold War to one side or the other. Here's the best (and so well written I'm just going to quote it) 'back of the envelope'analysis I've read. From Postwar, by Tony Judt.
"In Europe the Cold War began not after the Second World War but following the end of the First... .The years 1941-45 were just an interlude in an international struggle between Westerns democracies and Soviet totalitarianism, a struggle whose shape was obscured but not fundamentally altered by the threat posed to both sides by the rise of Fascism and Nazism at the heart of the continent.
"It was Germany that brought Russia and the West together in 1941, much as it had succeeded in doing before 1914. But the alliance was foredoomed. From 1918-34 the Soviet strategy in central and western Europe—splitting the Left and encouraging subversion and violent protest—helped shape an image of ‘Bolshevism’ as fundamentally alien and hostile. Four years of troubled and controversial ‘Popular Front’ alliances did something to dispel this impression, despite the contemporary trials and mass murders in the Soviet Union itself. But the Molotov-Ribbentrop Pact of August 1939, and Stalin’s collaboration with Hitler in his dismemberment of their common neighbours the following year, considerably undermined the propaganda gains of the Popular Front years. Only the heroism of the Red Army and Soviet citizens in the years 1941-45, and the unprecedented crimes of the Nazis, helped dispel these earlier memories.
"As for the Soviets, they never lost their distrust of the West—a distrust whose roots go back far beyond 1917, of course, but which were well irrigated by Western military intervention during the civil war of 1917-21, by the Soviet Union’s absence from international agencies and affairs for the next fifteen years, by the well-founded suspicion that most Western leaders preferred Fascists to Communists if forced to choose, and by the intuition that Britain and France especially would not be sorry to see the Soviet Union and Nazi Germany engage in mutually destructive conflict to others’ advantage... "
From the same source: "... . At least through mid-1946, many US leaders spoke and acted as though they truly believedin the continuation of their wartime partnership with Stalin. Even Lucretius Patrascanu, a senior figure in the Romanian Communist leadership (and later victim of a show trial in his own country), was moved to comment, at the time of the Paris Peace Treaty negotiations in the summer of 1946, that ‘[t]he Americans are crazy. They are giving even more to the Russians than [they] are asking and expecting.'"
This changed quickly. American positions hardened after the Berlin Blockade.